T Cell Flashcards
What are T cells?
Lymphocytes with diverse antigen specific receptors
What happens if you don’t have T cells?
Highly susceptible to viral, bacterial and fungal infections
What is an example of a disease when you don’t have T cells?
Severe Combined Immunodeficiency (SCID)
What is SCID?
A genetic mutation that affects the development of T cells
What do helper T cells do?
CD4+
Produce cytokines to direct a variety of immune responses
What do cytotoxic T cells do?
CD8+
Directly kill infected cells
How many antigen specific receptors do T cells have?
1
How many antigen specific receptors do B cells have?
2
What do T cell receptors recognise?
Processed peptide antigen presented by MHC molecules
What does TCR bind to?
Both peptide antigen and MHC molecule
Where T cell development?
In the thymus
What are the two important steps in T lymphocyte development?
- Make a T cell receptor and test it for usefulness and self reactivity
- Express CD4 and/or CD8 and determine which MHC class it is
What is double positive in T cells?
Positive selection - when both CD4 and CD8 are expressed
What is single positive T cells?
Negative selection - when CD4 or CD8 are expressed
What do double positive thymocytes interact with?
The cortical thymic epithelia cells
What occurs during positive selections?
Did it rearrange a useful TCR?
Will it be a CD4 or CD8 T cell?
How many thymocytes pass selection?
2%
What do single positive thymocytes interact with?
Medullary thymic epithelial cells and dendrite cells
What occurs during negative selection?
Did it rearrange a self-reactive TCR?
Why is negative selection important?
It prevents highly self reactive cells from entering the blood stream
What do mTECs do?
Promiscuously express tissue restricted antigens
What do cytotoxic T cells do after activation?
Differentiate into effector cells and kill infected cells
What are effector cells?
Cells that have the license to kill
What is perforin-granzyme mediated killing?
Perforin creates pores in the target cell membrane, allowing granzymes to enter and trigger cell death
